Geometrical constraints upon the unipolar model of V407 Vul and RXJ0806.3+1527

Abstract

V407 Vul and RX J0806.3+1527 are X-ray emitting stars with X-ray light curves that are 100% modulated on periods of 569 and 321 seconds respectively. These periods and no others are also seen at optical and infra-red wavelengths. These properties have led to the suggestion that the periods are the orbital period of ultra-compact pairs of white dwarfs. There are two main double white dwarf models: the unipolar inductor model analogous to the Jupiter-Io system and the direct impact model analogous to Algol. In this paper we consider geometrical constraints on the unipolar inductor model, in particular what parameter values (component masses, orbital inclination and magnetic co-latitude) can describe the X-ray and optical light curves. We find that for a dipole field on the primary star, the unipolar inductor model fails to match the data on V407 Vul for any combination of parameters, and can only match RX 0806.3+1527 if the sparser set of observations of this star have been unluckily timed.

arXiv comment7 pages, 7 figures (figure 6 has been compressed), accepted for publication in MNRAS

References in corpus (13)

• Population synthesis for double white dwarfs. II. Semi-detached systems: AM CVn stars
• V407 Vul: a direct impact accretor
• RXJ0806.3+1527: a double degenerate binary with the shortest known orbital period (321s)
• An electrically powered binary star?
• RX J0806+15: the shortest period binary?
• Detection of the optical counterpart of the proposed double degenerate polar RX J1914+24
• Optical/Infrared spectroscopy and photometry of the short period binary RX J1914+24
• Evidence for Orbital Decay of RX J1914.4+2456: Gravitational Radiation and the Nature of the X-ray Emission
• Spin up in RX J0806+15 - the shortest period binary
• Face-on, stream-fed intermediate polars: an alternative model for RX J1914.4+2456 and RX J0806.3+1527
• CHANDRA Observations of V407 Vul: Confirmation of the Spin-up
• Unveiling the Nature of the 321 s Modulation in RX J0806.3+1527: Near-Simultaneous Chandra and VLT Observations
• Phase Coherent Timing of RX J0806.3+1527 with ROSAT and CHANDRA

Cited by in corpus (14)

• Concepts and status of Chinese space gravitational wave detection projects
• Spectroscopic Evidence for a 5.4-Minute Orbital Period in HM Cancri
• Precision X-ray Timing of RX J0806.3+1527 with CHANDRA: Evidence for Gravitational Radiation from an Ultracompact Binary
• ULTRACAM Photometry of the ultracompact binaries V407 Vul and HM Cnc
• The Turn-On of Mass Transfer in AM CVn Binaries: Implications for RX J0806+1527 and RX J1914+2456
• Period Changes in Ultra-compact Double White Dwarfs
• Source localizations with the network of space-based gravitational wave detectors
• SPH Simulations of Direct Impact Accretion in the Ultracompact AM CVn Binaries
• The influence of short term variations in AM CVn systems on LISA measurements
• Detection of gravitational wave mixed polarization with single space-based detectors
• Synthetic Direct Impact Light Curves of the Ultracompact AM CVn Binary Systems V407 Vul and HM Cnc
• A search for electron cyclotron maser emission from compact binaries
• Magnetic Interaction in Ultra-compact Binary Systems
• Parameter estimation for space-based gravitational wave detectors with ringdown signals